There seems to have been a backlash from users when Spotify (link below) required users to login with their FB accounts (perhaps only because they were paying customers?). Are users generally adversed to this? What has been your experience?
http://www.pcworld.com/article/240646/spotify_adds_facebook_requirement_angering_users.html
It depends on the site. People aren’t particularly trustful of facebook, though they use it all the same.